Surfboard rails extend along opposed lateral edges of a surfboard from the nose to the tail of the board. The rails serve to guide water around the board when the board encounters a wave. Such guiding serves to control the board by providing edgewise board bite or slicing into a water wall allowing a board carrying a rider to have horizontal support from a partly vertical wall of water. In the past, it was thought that harder rails allow better board edge support from a wave. Hard rails were thought to have less resistance in cutting through the water, just like a sharp knife slices meat. Yet, rails have to be a compromise between slicing ability and buoyancy with hard rails having less buoyancy compared to soft rails.
U.S. Pat. No. 9,809,284 to D. Hantz discloses a lightweight surfboard with a set of channels or grooves shaped into a top portion of the body of the surfboard. The channels or grooves comprise a pair of adjacent, axially extending elongated concave grooves that run along the length of the board, meeting at end points. The purpose of the grooves is to prevent the board from breaking due to bending of the surfboard while being ridden on the wave. FIG. 5 herein shows a single edgewise groove that is concave in cross section that is known in the prior art and used for surfboard control.
In U.S. Pat. No. 4,719,952 rails are described as presenting a low drag edge at an angle in contact with the surface of a wave much like the edges of a conventional snow ski. Rails are further described as essential for effective control of the surfboard in the water. The comparison of surfboard rails to hard edges of snow skis is consistent with the construction of prior art surfboards with rail hardness and thickness being principal variable factors.
An object of the invention was to devise an improved rail configuration that both improves floatation and improves surfboard control.